I wouldn't worry about it being something big at this point. 4 hours run time isn't very long, and gremlins can take some time to flush out. Could be as easy as something loose that worked on out in the run time.

I had a slow to a stop deal a few weeks back. It was the VR. I also heard a real loud pop when it fully died. Do you have voltage in the rest of the car?

I want my fair share